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Abstract:

Embodiments relate to current difference sensors, systems and methods. In
an embodiment, a current difference sensor includes first and second
conductors arranged relative to one another such that when a first
current flows through the first conductor and a second current, equal to
the first current, flows through the second conductor, a first magnetic
field induced in the first conductor and a second magnetic field induced
in the second conductor cancel each other at a first position and a
second position; and first and second magnetic field sensing elements
arranged at the first and second positions, respectively.

Claims:

1. A current difference sensor comprising: first and second conductors
arranged relative to one another such that when a first current flows
through the first conductor and a second current, equal to the first
current, flows through the second conductor, a first magnetic field
caused by the first current and a second magnetic field caused by the
second current cancel each other at a first position and a second
position; and first and second magnetic field sensing elements arranged
to detect the first and second magnetic fields.

2. The sensor of claim 1, further comprising circuitry coupled to the
first and second magnetic field sensing elements to determine a
difference between the first and second magnetic fields.

3. The sensor of claim 1, further comprising a die, the first and second
magnetic field sensing elements arranged on a first surface of the die.

4. The sensor of claim 3, wherein the die is arranged between the first
and second conductors.

5. The sensor of claim 4, wherein the first conductor is disposed in a
first plane, the second conductor is arranged in a second plane and the
die is arranged in a third plane, the first and second planes being
substantially parallel.

6. The sensor of claim 5, wherein the third plane is substantially
parallel with the first and second planes.

7. The sensor of claim 6, wherein the first surface of the die is
substantially equidistantly spaced between the first and second
conductors.

8. The sensor of claim 7, wherein the first and second conductors are
laterally asymmetrically arranged with respect to one another.

9. The sensor of claim 8, wherein the first and second conductors are
laterally asymmetrically arranged by less than about 1 millimeter.

10. The sensor of claim 8, wherein a lateral dimension of each conductor
differs by less than about 1 millimeter.

11. The sensor of claim 3, further comprising at least one additional
magnetic field sensing element arranged on the first surface of the die.

12. The sensor of claim 11, further comprising a plurality of magnetic
field sensing elements, the first and second magnetic field sensing
elements being two of the plurality.

13. The sensor of claim 12, wherein the first and second magnetic field
sensing elements are selected from the plurality of magnetic field
sensing elements for having a low sensitivity to a sum of the first
current and the second current and a high sensitivity to a difference
between the first current and the second current.

14. The sensor of claim 1, further comprising circuitry coupled to the
first and second magnetic field sensing elements and configured to
calculate a sum and a difference of the first and second currents based
on sensed information from the magnetic field sensing elements.

15. A method comprising: inducing a first current to flow in a first
conductor; inducing a second current to flow in a second conductor;
arranging the first and second conductors such that at least one
component of a total magnetic field caused by the first and second
currents is approximately zero in at least two locations when the first
and second currents are approximately equal; positioning magnetic field
sensors in the at least two locations; and determining a difference
between the first and second currents based on sensed magnetic fields.

16. The method of claim 15, further comprising determining a sum of the
first and second currents.

17. The method of claim 15, further comprising arranging the first
conductor in a first plane and the second conductor in a second plane
substantially parallel to the first plane.

18. The method of claim 17, further comprising arranging a silicon die
between the first and second conductors.

19. The method of claim 18, further comprising arranging a plurality of
magnetic field sensors on a top surface of the silicon die, the top
surface being positioned substantially midway between the first and
second conductors.

20. The method of claim 18, wherein arranging further comprises laterally
asymmetrically arranging the first conductor relative to the second
conductor.

21. The method of claim 20, further comprising trimming by selecting,
from the plurality, first and second magnetic field sensors having the
least sensitivity to a sum of the first current and the second current.

22. A method comprising: arranging a first conductor spaced apart from
and substantially parallel to a second conductor; arranging a die
proximate the first and second conductors; and arranging a plurality of
magnetic field sensing elements on a first surface of the die to detect
magnetic fields caused by first and second currents in the first and
second conductors, respectively, and determine a difference between the
first and second currents based on the magnetic fields.

23. The method of claim 22, wherein arranging the first conductor further
comprises laterally asymmetrically positioning the first conductor with
respect to the second conductor.

24. The method of claim 22, wherein arranging a die further comprises
arranging the die substantially parallel to the first and second
conductors.

25. The method of claim 22, further comprising inducing current to flow
in at least one of the first and second conductors.

Description:

TECHNICAL FIELD

[0001] The invention relates generally to current sensors and more
particularly to current difference sensors suitable, for example, for
sensing small current differences.

BACKGROUND

[0002] Conventional current difference sensing systems often use a
ring-shaped ferrite. Two wires are coupled to the ring such that two
currents flow through the ring in opposite directions and their flux
contributions cancel. If the two currents are different, a net flux is
carried by the ferrite, which can be detected by a secondary winding and
processed electronically.

[0003] While such systems can be effective for detecting current
differences, they provide only limited information. For example, they can
detect whether |I1-I2|>threshold but do not provide any reliable
information regarding I1+I2 or I1-I2.

[0004] Therefore, there is a need for improved current difference sensing
systems and methods.

SUMMARY

[0005] Current difference sensors, systems and methods are disclosed. In
an embodiment, a current difference sensor comprises first and second
conductors arranged relative to one another such that when a first
current flows through the first conductor and a second current, equal to
the first current, flows through the second conductor, a first magnetic
field caused by the first current and a second magnetic field caused by
the second current cancel each other at a first position and a second
position; and first and second magnetic field sensing elements arranged
to detect the first and second magnetic fields.

[0006] In an embodiment, a method comprises inducing a first current to
flow in a first conductor; inducing a second current to flow in a second
conductor; arranging the first and second conductors such that at least
one component of a total magnetic field caused by the first and second
currents is approximately zero in at least two locations when the first
and second currents are approximately equal; positioning magnetic field
sensors in the at least two locations; and determining a difference
between the first and second currents based on sensed magnetic fields.

[0007] In an embodiment, a method comprises arranging a first conductor
spaced apart from and substantially parallel to a second conductor;
arranging a die proximate the first and second conductors; and arranging
a plurality of magnetic field sensing elements on a first surface of the
die to detect magnetic fields caused by first and second currents in the
first and second conductors, respectively, and determine a difference
between the first and second currents based on the magnetic fields.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The invention may be more completely understood in consideration of
the following detailed description of various embodiments of the
invention in connection with the accompanying drawings, in which:

[0009] FIG. 1 depicts a side cross-sectional view of a current difference
sensor according to an embodiment.

[0010] FIG. 2 depicts a side cross-sectional view of a current difference
sensor according to an embodiment.

[0011]FIG. 3 depicts a side cross-sectional view of a current difference
sensor according to an embodiment.

[0012] FIG. 4 depicts a graph of magnetic fields for various die and
conductor arrangements according to an embodiment.

[0013]FIG. 5 depicts a side cross-sectional view of a current difference
sensor according to an embodiment.

[0014] FIG. 6 depicts a side cross-sectional view of a current difference
sensor according to an embodiment.

[0015] FIG. 7 depicts a side cross-sectional view of a current difference
sensor according to an embodiment.

[0016] FIG. 8 depicts a side cross-sectional view of a current difference
sensor according to an embodiment.

[0017]FIG. 9 depicts orthogonal magnetic field sensor elements according
to an embodiment.

[0018] FIG. 10A depicts a side cross-sectional view of a current
difference sensor according to an embodiment.

[0019]FIG. 10B depicts a top plan view of the current difference sensor
of FIG. 10A.

[0020] FIG. 11 depicts a side cross-sectional view of a current difference
sensor according to an embodiment.

[0021] FIG. 12 depicts a side cross-sectional view of a current difference
sensor according to an embodiment.

[0022] FIG. 13 depicts a top plan view of a current difference sensor
according to an embodiment.

[0023] FIG. 14A depicts a top plan view of a current difference sensor
conductor according to an embodiment.

[0024] FIG. 14B depicts a top plan view of a current difference sensor
conductor according to an embodiment.

[0025] FIG. 14C depicts a top plan view of the current difference sensor
conductors of FIGS. 14A and 14B.

[0026] FIG. 14D is a side cross-sectional view of the current difference
sensor of FIGS. 14A-14C.

[0027] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of example in
the drawings and will be described in detail. It should be understood,
however, that the intention is not to limit the invention to the
particular embodiments described. On the contrary, the intention is to
cover all modifications, equivalents, and alternatives falling within the
spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

[0028] Embodiments relate to current difference sensors. In various
embodiments, a current difference sensor can compare two currents and
detect a difference therebetween. In one embodiment, the detectable
difference can be as small as about 10 mA for currents in a range of
about zero to about 30 A, though this can vary in other embodiments.
Additionally, embodiments can provide reduced delay times, such as below
about 1 microsecond, and provide information regarding I1+I2 as well as
I1-I2. Further, embodiments are small in size, robust against
interference and inexpensive.

[0029] Embodiments comprise two conductors arranged such that when equal
currents pass therethrough, magnetic field contributions of each
conductor cancel at points at which magnetic field sensor elements,
sensing the same magnetic field components, can be arranged. Unequal, or
difference, currents can then be detected, with the components subtracted
in order to cancel homogeneous background fields.

[0030] Referring to FIG. 1, an embodiment of a current difference sensor
100 is depicted. Sensor 100 comprises two conductors 102 and 104 spaced
apart from one another on two different planes or levels. A die 106 is
arranged therebetween on a third plane or level, and two magnetoresistors
(MRs) 108 and 110 are disposed on die 106. MRs 108 and 110 are spaced
apart from on another and disposed on a plane approximately midway
between conductors 102 and 104 and therefore between currents I1 and I2
in conductors 102 and 104, respectively. In embodiments, MRs 108 and 110
can comprise anisotropic MRs, giant MRs or some other MR effect
technology.

[0031] Because of assembly tolerances and other factors, however, it is
virtually impossible in practice to position MRs 108 and 110 exactly
midway between conductors 102 and 104. The resulting magnetic fields, Bx1
on MR 108 and Bx2 on MR 110, therefore are as follows:

Bx1=(K+dK)*I1-(K-dK)*I2

Bx2=(K'+dK')*I1-(K'-dK')*I2

Bx1-Bx2=(K-K')*(I1-I2)+(dK-dK')*(I1+I2)

The difference measurement, Bx1-Bx2, is thus corrupted by the sum of the
currents, I1+I2. One solution to this issue would be to provide several
MRs on the top surface of die 106 and then select the MRs which have the
best suppression of (I1+I2). Because this is generally not a good
solution, another solution is to add Hall plates to sensor 100, with a
first, H1, arranged proximate MR 108 and a second, H2, arranged proximate
MR 110. Then:

H2-H1=Kz*(I1+I2)

which leads to:

I1-I2=[(Bx1-Bx2)/(K-K')]-[(dK-dK')*(H2-H1)/(Kz*(K-K'))]

An advantage of this configuration is that it has a low resistance
because conductors 102 and 104, in an embodiment, are simple straight
bars. Additionally, information regarding I1+I2 and I1-I2 can be
obtained.

[0032] Another embodiment is depicted in FIG. 2, in which die 106 is
mounted in a slightly tilted orientation with respect to the planes of
conductors Il and I2. The tilt angle of die 106 can vary but is generally
configured to be larger than worst-case assembly tolerances.
Additionally, a plurality of MRs 108 and 110 are arranged on the top
surface of die 106. While only MRs 108 and 110 are visible in FIG. 2,
this embodiment of sensor 100 comprises additional MRs arranged in a grid
on the top surface of die 106, spaced apart by, for example, 25
micrometers along the x-axis. The spacing can vary in other embodiments.
After assembly of sensor 100, the signals of all MRs 108 and 110 as well
as the grid are tested, and those having the lowest sensitivity to I1+I2
are selected.

[0033] Another embodiment is depicted in FIG. 3, in which a small,
generally arbitrary lateral asymmetry is introduced between conductors
102 and 104. As in the embodiment of FIG. 2, a grid of MRs 108 and 110
and others not visible in FIG. 3 is arranged on the top surface of die
106, and those having the lowest sensitivity to I1+I2 are selected. In an
embodiment, conductors 102 and 104 are each about 6 mm by about 1 mm and
are shifted relative to each other by less than about 1 mm in the
x-direction in embodiments, such as by about 0.2 mm in one embodiment.

[0034] Because of assembly tolerances, it is assumed, for purposes of this
example embodiment, that die 106 is tilted by about 1.5 degrees around
the symmetry center of conductors 102 and 104. Referring also to FIG. 4,
the magnetic field Bx for five different scenarios is depicted, for all
of which I1=I2=30 A and z=0.5 mm. For scenario 1, die 206 is shifted 100
μm (from center) toward conductor 104. For scenario 2, die 206 is
shifted 50 μm (from center) toward conductor 104. For scenario 3, die
206 is at center. For scenario 4, die 206 is shifted 50 μm toward
conductor 102. For scenario 5, die 206 is shifted 100 μm toward
conductor 102.

[0035] In back-end test, after die 106 is mounted between conductors 102
and 104, the voltage difference of MRs 108-108n and 110-110n arranged in
a grid on the top surface of die 106 as previously mentioned can be
measured. Note that the grids of MR108-108n and MR110-110n may or may not
overlap in embodiments. As depicted in FIG. 4, the respective grids do
not overlap. The two MRs having the lowest sensitivity with respect to
(I1+I2) can be selected. FIG. 4 shows five curves 1-5 corresponding to
five different scenarios 1-5, where each curve represents the magnetic
field parallel to the die surface versus x-position. For scenario 1, FIG.
4 shows that the fired on MR 108n is equal to the field on MR 110n, so
that the difference is zero. Thus, in end-of-line testing, sensor 100
could be trimmed by selecting MR108n and MR110n. For scenario 5 in FIG.
4, the field on MR 108 is the same as the one on MR 110. Therefore, these
two MRs can be selected during the trimming process. This makes it
possible in embodiments to trim sensor 100 such that it does not respond
to (I1+I2) but rather only (I1-I2). Any mismatch of the MRs is also
trimmed by this procedure.

[0036] Referring again to FIG. 3, the concept can be generalized.
Conductors 102 and 104 are of similar shape and carry the same current
such that midway between the two, the respective magnetic fields of
conductors 102 and 104 cancel to a large extent, in the sense that the
magnitude of the total field is much less, e.g. by a factor of 100 or
1,000, than the magnitude of the fields caused by a single conductor.
Conductors 102 and 104 are formed to have a small asymmetry such that the
lateral magnetic field caused by identical currents in both conductors
102 and 104 exhibits a small peak at a certain position x for all
assembly tolerances between conductors 102 and 104 and die 106. For all
tolerances, there is at least one MR (108 or 110) to the left and one MR
(110 or 108) to the right of the peak, with the lateral magnetic field
identical on both MRs 108 and 110.

[0037] The asymmetry depicted in FIG. 3 is obtained by shifting conductor
104 slightly laterally with respect to conductor 102. In another
embodiment, conductor 104 could be made slightly wider than conductor 102
such that the right edges of each are positioned as in FIG. 4 with the
left edges flush. In yet another embodiment, the cross-sectional area of
one of the conductors 102 or 104 can be tapered such that it is thicker
(in the vertical direction with respect to the orientation of the drawing
on the page) at the left side than the right, or vice-versa. Or, both
conductors 102 and 104 can be tapered yet positioned such that the
thicker end of one is flush with the thinner end of the other.

[0038] Other embodiments are also possible. In the embodiment of FIG. 5,
sensor 100 comprises first and second conductors 102 and 104 mounted to a
bottom side of a printed circuit board (PCB) 114 to isolate the
conductors 102 and 104 from die 106, which is mounted to a top side of
PCB 114. In embodiments, PCB 114 can be replaced by some other
non-conducting structure comprising, for example, glass, porcelain or
some other suitable material. Three MRs 108, 110 and 112 are mounted to a
top side of die 106. In an embodiment, MRs 108 and 110 are separated by
1.25 mm, and MRs 110 and 112 are separated by 1.25 mm, such that MRs 108
and 112 are separated by 2.5 mm, though these dimensions can vary in
embodiments. With currents in conductors 102 and 104 flowing into the
drawing plane as depicted in FIG. 5, MR 108 detects a strong field from
the current through conductor 102 and weak field from the current through
conductor 104, whereas MR 112 responds more strongly to current through
conductor 104 than through conductor 102. MR 110 responds equally to the
currents in conductors 102 and 104 such that the field on MR 110 is
proportional to the sum of the currents in conductors 102 and 104,
whereas the fields on the other MRs 108 and 112 are neither proportional
to pure sums nor pure differences of the currents but rather a
combination of both.

[0039] A challenge with the embodiment of FIG. 5 is balancing sensitivity
and saturation. High sensitivity is desired to measure small magnetic
fields, but efforts to increase sensitivity, such as reducing the
vertical distance between conductors 102 and 104 and MRs 108, 110 and 112
and/or the cross-sectional dimensions of conductors 102 and 104, can send
the MRs into saturation such that larger current differences can no
longer be detected. Such an embodiment can be suitable for various
desired applications, however.

[0040] Another embodiment is depicted in FIG. 6, in which sensor 100
comprises three conductors 102, 103 and 104. Center conductor 103 can be
used to "tune" sensor 100 such that positions are obtained without a
magnetic field, and MRs 108 and 110 can then be arranged accordingly to
see no net field. In an embodiment, conductors 102 and 104 are each about
1.2 mm by about 1.2 mm, and conductor 103 is about 1.7 mm by about 1.7
mm. Die 106 is coupled to a wafer 116, which is about 200 μm thick and
comprises glass or porcelain or some other suitable material in
embodiments and includes through-vias 120. Vias 120 are filled with a
conductor, such as a nano-paste, in embodiments. In one embodiment, the
silicon of die 106 is ground down to about 30 μm and adhesively bonded
at its top side to wafer 116. Die(s) 106 can then be cut or otherwise
formed into rectangles, and the bottom side(s) and sidewalls coated with
a low-temperature dioxide or silicon oxide (SiOx). In an embodiment, the
dioxide is about 15 μm thick. MRs 108 and 110 are spaced apart about
x=2 mm and are separated from the top side of conductors 102-104 by about
z=50 μm in an embodiment. Conductors 102-104, die 106 and wafer 116
are covered by a mold compound 118.

[0041] In an embodiment, current flows into the drawing plane (as depicted
in FIG. 6) through center conductor 103 and out of the drawing plane
(again, as depicted in FIG. 6) through outer conductors 102 and 104, each
of which carries about half of the current. MR sensors 108 and 110 form a
bridge and are arranged at locations where the magnetic fields of
conductor 103 and either of conductors 102 and 104 cancel at equal
currents.

[0042] A further adaptation of sensor 100 of FIG. 6 is depicted in FIG. 7,
in which sensor 100 comprises a dual-die package. One MR 108 is coupled
to an upper die 106a, and another MR 110 is coupled to a lower die 106b,
with MRs 108 and 110 located on a common axis in an embodiment.
Conductors 102 and 104 are similar to conductor 103 in an embodiment and
are about 1.7 mm by about 1.7 mm. Such an embodiment can provide
advantages with respect to obtaining information about (I1+I2) and
improve cancelation of background of fields. In an embodiment of sensor
100 of FIG. 7, wafers 116 can be omitted.

[0043] It can be difficult, because of assembly tolerances and other
factors, to arrange MRs 108 and 110 on the same axis, represented by a
dashed vertical line in FIG. 7. Therefore, another, potentially more
robust embodiment of sensor 100 depicted in FIG. 8 can address this
challenge by including additional MRs 109 and 111. In an embodiment,
conductors 102 and 104 are each about 0.9 mm by about 1.7 mm, and
conductor 103 is about 1.7 mm by about 1.7 mm. Conductors 102-104 are
cast into glass 122 in an embodiment, and contacts 124 couple PCBs 114a
and 114b. MRs 108-111 are separated from conductors 102-104 by z=about
250 μm in embodiments.

[0044] In operation, current I1 flows through conductor 103, while current
I2 is split into two halves which each flow through one of conductors 102
and 104 in the opposite direction of current I1. The signals of MRs 108
and 109 are added, as are those of MRs 110 and 111, with the latter then
subtracted from the former. Because MRs 108 and 110 experience strong I1
fields, while MRs 109 and 111 experience strong I2 fields of the opposite
polarity of I1, lateral positioning shifts of the MRs 108-111 are
compensated for. Casting conductors 102-104 in glass helps to avoid
dimensional changes over the lifetime thereof due to moisture and other
factors.

[0045] A potential drawback of the embodiment of FIG. 8, however, is the
expense of a dual-die solution. In various embodiments, temperature can
also be an issue. To provide temperature compensation, orthogonal MRs can
be added, an embodiment of which is depicted in FIG. 9. FIG. 9 depicts
two MRs 108 and 110, each with an orthogonal MR 108' and 110' forming
half-bridges. Embodiments comprising additional MRs, such as grids of MRs
as discussed herein, can similarly comprise additional orthogonal MRs. In
operation, and with the barber poles as depicted in FIG. 9, MRs 108 and
110 are sensitive to weak fields in the x-direction, while MRs 108' and
110' are sensitive to weak fields in the -x-direction. The close
arrangements of MRs 108 and 108', and 110 and 110', ensures that each
sees the same magnetic field and temperature. The signals of each
half-bridge, U1 and U2, are therefore temperature compensated.

[0046] Another embodiment of a sensor 100 is depicted in FIG. 10. In this
embodiment, sensor 100 comprises a single die 106, with three MRs 108,
109 and 100 mounted on a top surface thereof. Although the dimensions can
vary in embodiments, in one embodiment die 106 can be about 4 mm by about
1.75 mm, with a thickness of about 200 μμm, and MRs 108 and 110 are
spaced apart by x=about 4 mm. Four conductors 102, 103, 104 and 105 are
cast into glass 122, similar to the embodiment of FIG. 8, with a top
surface of conductors 102-105 spaced apart from MRs 108-110 by z=about
250 μm in an embodiment. As depicted in FIG. 10B, conductors 102-105
comprise conductor portions, with conductors 102 and 105, along with a
connecting portion 101, forming a first generally U-shaped conductor
element, and conductors 103 and 104, along with a connecting portion 107,
forming a second generally U-shaped conductor element. A cross-section of
each of conductors 102-105 as depicted in FIG. 10A is about 1.7 mm by
about 1.7 mm in an embodiment. In FIG. 10B, the length of conductors 102
and 105 is y=about 10 mm, with a width of x=about 8.3 mm of connecting
portion 101. A separation distance between adjacent ones of the
conductors 102-15 is x=about 0.5 mm in the embodiment depicted.

[0047] Advantages of the embodiment of FIG. 10 include a single die, which
is less expensive and provides easier assembly, because it does not
require pins for communication with a second die. A single die also
provides fewer opportunities for mismatch of the MR sensor elements as
well as improved temperature homogeneity. The MRs of FIG. 10 can comprise
orthogonal MRs, such as are depicted in FIG. 9 and discussed above, in
embodiments.

[0048] Sensor system 100 depicted in FIG. 11 is similar to that of FIG. 10
but comprises a triple Hall element 128, 129 and 130 system in addition
to MRs to measure the sum of the currents I1+I2. Advantages of the
embodiment of FIG. 11 include increased robustness against disturbances
and improved tamper-resistance.

[0049] On the other hand, Hall elements 128-130 should be positioned
closer to conductors 102-105. Therefore, another embodiment (not
depicted) comprises Hall elements 128-130 on a bottom side of die 106 and
MRs on a top side of die 106. Die 106 can be about 200 μm thick in
such an embodiment.

[0050] Alternatively, AMRs 108 and 110 can be implemented to measure
I1+x*I2 (x<<1), as depicted in the embodiment of FIG. 12. AMRs 108
and 100 can be positioned on a top surface of die 106, which can be about
200 μm thick in an embodiment, such that a separation distance between
AMRs 108 and 110 and top surfaces of conductors 102-15 is z=about 250
μm. Such a system is generally robust against background fields,
though not as robust as the triple Hall embodiment of FIG. 11. The small
damping effect, x, is due to the distance between conductors 102 and 105,
through which current I2 flows, and AMRs 108 and 110.

[0051] In the embodiment of FIG. 13, a return path for I2 is omitted, such
that only three conductors 102-104 are implemented. The conductors
102-104, however, can be made wider, such as x=about 3.5 mm for each of
conductors 103 and 104 and x=about 6 mm for conductor 102, and
dissipation reduced by about 50%. A separation distance between
conductors 103 and 104 is still x=about 0.5 mm in an embodiment, and a
length of conductor 102 is y=about 10 mm in an embodiment.

[0052] Yet another embodiment is depicted in FIG. 14, in which sensor
system 100 comprises a multi-level conductor 132, at least somewhat
similar to the embodiments discussed above with respect to FIGS. 1-4.
Conductor 132 (FIG. 14C) comprises a first layer 134 (FIG. 14A) and a
second layer 136 (FIG. 14B) in an embodiment. In an embodiment, isolation
layers 138 are positioned between die 106 and conductor level 136, and
between conductor level 136 and conductor level 134.

[0053] Various embodiments of current and current difference sensing and
determination systems are disclosed. Embodiments can be advantageous by
providing single sensor systems capable of measuring current flow (I1+I2)
and leakage currents (I1-I2) while also being small in size, robust
against interference and inexpensive when compared with conventional
difference current sensor systems. Embodiments can also be combined with
an isolated voltage sensor in order to obtain a full power measurement.

[0054] Various embodiments of systems, devices and methods have been
described herein. These embodiments are given only by way of example and
are not intended to limit the scope of the invention. It should be
appreciated, moreover, that the various features of the embodiments that
have been described may be combined in various ways to produce numerous
additional embodiments. Moreover, while various materials, dimensions,
shapes, configurations and locations, etc. have been described for use
with disclosed embodiments, others besides those disclosed may be
utilized without exceeding the scope of the invention.

[0055] Persons of ordinary skill in the relevant arts will recognize that
the invention may comprise fewer features than illustrated in any
individual embodiment described above. The embodiments described herein
are not meant to be an exhaustive presentation of the ways in which the
various features of the invention may be combined. Accordingly, the
embodiments are not mutually exclusive combinations of features; rather,
the invention may comprise a combination of different individual features
selected from different individual embodiments, as understood by persons
of ordinary skill in the art.

[0056] Any incorporation by reference of documents above is limited such
that no subject matter is incorporated that is contrary to the explicit
disclosure herein. Any incorporation by reference of documents above is
further limited such that no claims included in the documents are
incorporated by reference herein. Any incorporation by reference of
documents above is yet further limited such that any definitions provided
in the documents are not incorporated by reference herein unless
expressly included herein.

[0057] For purposes of interpreting the claims for the present invention,
it is expressly intended that the provisions of Section 112, sixth
paragraph of 35 U.S.C. are not to be invoked unless the specific terms
"means for" or "step for" are recited in a claim.